Organising data & statistical charts · Ages 12–13
Compound bar charts
Read the key, then compare month by month.
How to do it
Method
Read the key, then compare month by month
March: A 40, B 25, a difference of 40 − 25 = 15
Another way
Copy it into a table
A: 40, 35, 50; B: 25, 45, 30
In full
A compound bar chart stands two bars side by side for each category (each month, say), with a key telling the two sets apart, so they can be compared item by item. To read it, use the key to see which bar is which, then read across from a bar's top to the scale. To compare the two in one month, subtract one height from the other; for the month with the greatest difference, work out each month's and compare, or look straight for the pair of bars furthest apart. For one set's total, add its bars' values. Or copy the chart into a two-row table first and work from that. A percentage = part ÷ total × 100%.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
The compound bar chart shows how many boxes of ice cream Shop A and Shop B sold in four months. How many did Shop A sell in June?
Show the answer and working
Answer: 60
The key shows Shop A as the first bar. In June its top is level with 60.
Example 2
The compound bar chart shows a club's new members in four months (male and female). In how many of the months did more women than men join?
Show the answer and working
Answer: 0
Compare the two bars month by month from January: the female bar (the second) is taller in 0 months.
Example 3
The compound bar chart shows how many boxes of ice cream Shop A and Shop B sold in four months. In which month was the gap between them greatest?
- A. April
- B. March
- C. February
- D. January
Choose the right answer
Show the answer and working
Answer: B. March
Work out each month's gap; the greatest is 30 boxes. Not the tallest bar, but the two bars furthest apart.
Practice questions to try
Try these 5; the answers are at the end. For a whole worksheet, see VIP worksheets below.
1.The compound bar chart shows a club's new members in four months (male and female). How many new female members joined in the four months?
Answer:
2.The compound bar chart shows a restaurant's bookings in four months, last year and this year. In which month were this year's bookings the most?
- A. September
- B. October
- C. December
- D. November
Choose the right answer
Answer:
3.The compound bar chart shows how many boxes of ice cream Shop A and Shop B sold in four months. How many did Shop A sell in April?
Answer:
4.The compound bar chart shows how many boxes of ice cream Shop A and Shop B sold in four months. In which month was the gap between them greatest?
- A. February
- B. May
- C. March
- D. April
Choose the right answer
Answer:
5.The compound bar chart shows how many boxes of ice cream Shop A and Shop B sold in the four months from April. In how many of the months did the two shops sell more than 300 boxes between them?
Answer:
All the answers
- 1. 950
- 2. C. December
- 3. 300
- 4. A. February
- 5. 3
VIP practice notes and papers
Aimed at tests and exams: questions on this topic, new every time, to print or save as a PDF.
- Practice notes: The key point, worked examples step by step, then questions of the same kind to follow, hints fading
- Practice paper: Set out in parts like a school paper, marked, with answers and full working
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